This invention relates to a communications network comprising two or more network nodes (ISR1 to ISR3) each provided with a Layer 2 switching element (SW1 to SW3) and a switch controller (SC1 to SC3) for controlling the respective Layer 2 switching element (SW1 to SW3), to a network node as (ISR1) for use in a communications network (MPLS-D comprising two or more network nodes (ISR1 to ISR3) each of which is provided with a Layer 2 switching element (Sw1 to SW3) and a switch controller (SC1 to SC3) for controlling the Layer 2 switching element (SW1 to SW3), to a switch controller for controlling a Layer 2 switching element (SW1) of a network node (ISR1) of a communications network (MPLS-D) comprising two or more network nodes (ISR1 to ISR3), and to a method of supporting shortcuts through a network node of a communications network comprising two or more network nodes (ISR1 to ISR3), with a switch controller (SC1) of the network node controlling a Layer 2 switching element (SW1) of the network node for supporting the shortcut.
The invention is based on a new multilayer routing concept for integrating, e. g., IP (=Internet Protocol) and ATM (=Asynchronous Transfer Mode), the multiprotocol label switching (MPLS) concept. This concept glues the Layer 2 functionalityxe2x80x94e.g., ATM switching xe2x80x94and the Layer 3 functionalityxe2x80x94e.g., IP routing. Network nodes which follow this concept are referred to as xe2x80x9cintegrated switch routersxe2x80x9d. They are composed of a Layer 3 router, a switch controller, and a Layer 2 switch.
One concept for implementing multiprotocol label switching is tag switching. This concept involves the use of routers for path selection. Tags are assigned to flows based on conventional routing information depending on network topology (xe2x80x9ctopology drivenxe2x80x9d). The process is not tied to the current traffic situation. In a tag switching network node, two tables must be provided: the normal routing table as is used in routers (IP address to output port), and a forwarding database which maps input tags and input ports to output tags and output ports.
Another concept for implementing multiprotocol label switching is the Ipsilon flow switching concept. The fundamental idea of this concept is to tie the routing intelligence (Layer 3) directly into the ATM switching process of the network nodes. Each data traffic is regarded as a flow. Forwarding decisions in Layer 3 are made only for the first data packets of a flow. The flow is then assigned a short identification and is forwarded at Layer 2.
The invention has for its object to provide a multilayer routing concept which can be better adapted to the specific requirements of a given communications network and to a particular network situation.
This object is attained by a communications network comprising two or more network nodes each provided with a Layer 2 switching element and a switch controller for controlling the respective Layer 2 switching element, wherein the switch controller is composed of several independent modules, namely a shortcut control module at least one trigger module, and at least one protocol module, that the at least one trigger module is designed to initiate the assignment of a shortcut, which is formed by a direct Layer 2 connection, to a Layer 3 forwarding relationship if respective predetermined criteria are satisfied, that the shortcut control module is designed to communicate with the respective Layer 2 switching element, initiating the assignment of data packets to shortcuts by marking data packets with a label assigned to the respective shortcut, and controlling the switching of shortcuts through the respective Layer 2 switching element, and that the at least one protocol module is designed to distribute labels to switch controllers of other network nodes of the communications network and thereby coordinate the assignment of labels to shortcuts.
The invention further resides in a network node, a switch controller for controlling a Layer 2 switching element, and a method of supporting shortcuts through a network node, for implementing the network described above.
The invention is predicated on recognition that each of the existing concepts is optimized for only one specific trigger event for establishing a Layer 2 connection. Because of the different natures of these concepts, a combination of different trigger mechanisms is not possible. It is therefore proposed to no longer regard the switch controller as a uniform functionality, but to construct it from several independent modules, namely a shortcut control module, at least one trigger module, and at least one protocol module. If respective predetermined criteria are satisfied, the trigger modules initiate the assignment of a shortcut, which is formed by a direct Layer 2 connection, to a Layer 3 forwarding relationship. The shortcut control module communicates with the respective Layer 2 switching element. It initiates the assignment of data packets to shortcuts by marking data packets with a label assigned to the respective shortcut, and controls the switching of shortcuts through the respective Layer 2 switching element. The protocol modules distribute labels to switch controllers of other network nodes of the communications network and thereby coordinate the assignment of labels to shortcuts.
The advantage of the invention lies in the fact that the combination of arbitrary trigger mechanisms within a communications network is made possible. Depending on the current network situation, an optimally adapted trigger mechanism can be used. The decoupling further permits a very simple integration of a plurality of different trigger mechanisms or a correspondingly simple subsequent expansion of network nodes by adding further trigger mechanisms.
Further advantageous aspects of the invention are defined in the subclaims.
Particularly advantageously, different types of trigger modules which provide different trigger mechanisms are provided in one switch controller. This enables different trigger mechanisms to operate in parallel in one network node.
Furthermore, it is particularly advantageous to provide uniform interfaces between the shortcut control modules, trigger modules, and protocol modules. This further reduces the cost and complexity of the software development.